Water wicking beds & boxes

A friend mentioned water wicking beds and it sounded interesting so I Googled. There’s a very good downloadable pdf file at this site and also some other good information.

Briefly, a water wicking bed is made by creating an underground reservoir of water contained by a waterproof container or liner below the surface. Water wicks up by capillary action to feed the plants. Watering is only needed when the plants have drawn up all the water in the reservoir. It seems like a very good way to conserve water and reduce the time spent watering as well. Two things I really need.

The bed can be constructed at ground level by building up a framework of timber or other material, and placing the waterproof plastic liner within this, or the soil can be dug out of the area down to a depth of 30 cm or so and the liner placed in the bottom of the hole so that it comes about a third of the way up the walls.

Once the liner is in place a length of slotted drainage pipe is laid the length of the bed with right-angle pieces at the ends and short plastic tubes as uprights. This is where the water is added.

If the dug-out soil is good quality it can be simply replaced, however the best option is to use a mix of good quality compost with added worms which aerate the medium and provide nutrient-rich castings. Of course, in a built-up bed new soil will have to be provided anyway. I think I prefer the built-up bed idea—no heavy digging involved.

A small-scale wicking bed can be created in a box. In my searching I found people who’d used polystyrene fruit boxes. I like this idea as the boxes can be located anywhere there’s room; I can envision a half dozen of them on our deck—just walk out the sliding door and pick the evening meal.

So I’ve started to put a few wicking boxes together for some growing trials. I’ve bought a few of those black plastic recycling crates; they’re 65 cm long, 45 cm wide, 25 cm deep and they hold 60 litres; bigger than your average poly box. I drilled a couple of overflow holes along each side and one at each end, about a third of the way up from the bottom. I dispensed with the drainage tube in the bottom and just put an upright plastic cylinder in the corner through which to add the water. I filled the bottom third of the box with coarsely mulched material and topped up with a mixture of partially rotted compost and soil. I added a few worms for good measure and filled the bottom with water via the tube until it ran out the overflow holes. I made 8 small depressions, filled them with moist peat moss and sowed a few tatsoi seed into each one. I’ll keep them damp untill they germinate and thin them eventually to one seedling at each spot.

Unfortunately, it’s heading towards winter here and there’ll be regular rain anyway so the wicking effect will be somewhat nullified by overhead rain, but come next summer and I’ll be really interested to see how they perform. Stay tuned for regular updates.